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e23730c7 | 1 | /************************************************************************** |
2 | * Copyright(c) 1998-1999, ALICE Experiment at CERN, All rights reserved. * | |
3 | * * | |
4 | * Author: The ALICE Off-line Project. * | |
5 | * Contributors are mentioned in the code where appropriate. * | |
6 | * * | |
7 | * Permission to use, copy, modify and distribute this software and its * | |
8 | * documentation strictly for non-commercial purposes is hereby granted * | |
9 | * without fee, provided that the above copyright notice appears in all * | |
10 | * copies and that both the copyright notice and this permission notice * | |
11 | * appear in the supporting documentation. The authors make no claims * | |
12 | * about the suitability of this software for any purpose. It is * | |
13 | * provided "as is" without express or implied warranty. * | |
14 | **************************************************************************/ | |
15 | ||
16 | //------------------------------------------------------------------------- | |
17 | // Implementation of the ESD V0 vertex class | |
18 | // | |
19 | // Origin: Iouri Belikov, IReS, Strasbourg, Jouri.Belikov@cern.ch | |
20 | //------------------------------------------------------------------------- | |
21 | #include <Riostream.h> | |
22 | #include <TMath.h> | |
23 | #include <TPDGCode.h> | |
24 | ||
25 | #include "AliESDv0.h" | |
26 | ||
27 | ClassImp(AliESDv0) | |
28 | ||
29 | AliESDv0::AliESDv0() : TObject() { | |
30 | //-------------------------------------------------------------------- | |
31 | // Default constructor (K0s) | |
32 | //-------------------------------------------------------------------- | |
33 | fPdgCode=kK0Short; | |
34 | fEffMass=0.497672; | |
35 | fChi2=1.e+33; | |
36 | fPos[0]=fPos[1]=fPos[2]=0.; | |
37 | fPosCov[0]=fPosCov[1]=fPosCov[2]=fPosCov[3]=fPosCov[4]=fPosCov[5]=0.; | |
38 | } | |
39 | ||
40 | Double_t AliESDv0::ChangeMassHypothesis(Int_t code) { | |
41 | //-------------------------------------------------------------------- | |
42 | // This function changes the mass hypothesis for this V0 | |
43 | // and returns the "kinematical quality" of this hypothesis | |
44 | //-------------------------------------------------------------------- | |
45 | Double_t nmass=0.13957, pmass=0.13957, mass=0.49767, ps=0.206; | |
46 | ||
47 | fPdgCode=code; | |
48 | ||
49 | switch (code) { | |
50 | case kLambda0: | |
51 | nmass=0.13957; pmass=0.93827; mass=1.1157; ps=0.101; break; | |
52 | case kLambda0Bar: | |
53 | pmass=0.13957; nmass=0.93827; mass=1.1157; ps=0.101; break; | |
54 | case kK0Short: | |
55 | break; | |
56 | default: | |
57 | cerr<<"AliV0vertex::ChangeMassHypothesis: "; | |
58 | cerr<<"invalide PDG code ! Assuming K0s...\n"; | |
59 | fPdgCode=kK0Short; | |
60 | break; | |
61 | } | |
62 | ||
63 | Double_t pxn=fNmom[0], pyn=fNmom[1], pzn=fNmom[2]; | |
64 | Double_t pxp=fPmom[0], pyp=fPmom[1], pzp=fPmom[2]; | |
65 | ||
66 | Double_t en=TMath::Sqrt(nmass*nmass + pxn*pxn + pyn*pyn + pzn*pzn); | |
67 | Double_t ep=TMath::Sqrt(pmass*pmass + pxp*pxp + pyp*pyp + pzp*pzp); | |
68 | Double_t pxl=pxn+pxp, pyl=pyn+pyp, pzl=pzn+pzp; | |
69 | Double_t pl=TMath::Sqrt(pxl*pxl + pyl*pyl + pzl*pzl); | |
70 | ||
71 | fEffMass=TMath::Sqrt((en+ep)*(en+ep)-pl*pl); | |
72 | ||
73 | Double_t beta=pl/(en+ep); | |
74 | Double_t pln=(pxn*pxl + pyn*pyl + pzn*pzl)/pl; | |
75 | Double_t plp=(pxp*pxl + pyp*pyl + pzp*pzl)/pl; | |
76 | ||
77 | Double_t pt2=pxp*pxp + pyp*pyp + pzp*pzp - plp*plp; | |
78 | ||
79 | Double_t a=(plp-pln)/(plp+pln); | |
80 | a -= (pmass*pmass-nmass*nmass)/(mass*mass); | |
81 | a = 0.25*beta*beta*mass*mass*a*a + pt2; | |
82 | ||
83 | return (a - ps*ps); | |
84 | ||
85 | } | |
86 | ||
87 | void AliESDv0::GetPxPyPz(Double_t &px, Double_t &py, Double_t &pz) const { | |
88 | //-------------------------------------------------------------------- | |
89 | // This function returns V0's momentum (global) | |
90 | //-------------------------------------------------------------------- | |
91 | px=fNmom[0]+fPmom[0]; | |
92 | py=fNmom[1]+fPmom[1]; | |
93 | pz=fNmom[2]+fPmom[2]; | |
94 | } | |
95 | ||
96 | void AliESDv0::GetXYZ(Double_t &x, Double_t &y, Double_t &z) const { | |
97 | //-------------------------------------------------------------------- | |
98 | // This function returns V0's position (global) | |
99 | //-------------------------------------------------------------------- | |
100 | x=fPos[0]; | |
101 | y=fPos[1]; | |
102 | z=fPos[2]; | |
103 | } | |
104 | ||
105 | Double_t AliESDv0::GetD(Double_t x0, Double_t y0, Double_t z0) const { | |
106 | //-------------------------------------------------------------------- | |
107 | // This function returns V0's impact parameter | |
108 | //-------------------------------------------------------------------- | |
109 | Double_t x=fPos[0],y=fPos[1],z=fPos[2]; | |
110 | Double_t px=fNmom[0]+fPmom[0]; | |
111 | Double_t py=fNmom[1]+fPmom[1]; | |
112 | Double_t pz=fNmom[2]+fPmom[2]; | |
113 | ||
114 | Double_t dx=(y0-y)*pz - (z0-z)*py; | |
115 | Double_t dy=(x0-x)*pz - (z0-z)*px; | |
116 | Double_t dz=(x0-x)*py - (y0-y)*px; | |
117 | Double_t d=TMath::Sqrt((dx*dx+dy*dy+dz*dz)/(px*px+py*py+pz*pz)); | |
118 | return d; | |
119 | } |